Update peer dependencies to Angular rc 4

[joshgarwood]

Current the peer dependencies target a fixed Angular rc.0 reference, which makes it such that this package can't be used in the latest version of Ionic 2, which targets RC 4. Or, better yet, make this an unfixed peer dependency so there won't be conflicts in the future (if that's possible).

Thanks!

[urish]

Hi, the peer deps specify "@angular/core": "^2.0.0-rc.0" which means it should be compatible with 2.x.x (including all later rc versions).

You can read more about it here: http://bytearcher.com/articles/semver-explained-why-theres-a-caret-in-my-package-json/